More particularly, the invention concerns devices known as “stand-up” wheelchairs, that allow their user to occupy a sitting position or a standing position. Such wheelchairs, as described in patent FR 2 769 830 for example, include a chassis supporting an articulated structure which includes a seat, a foot-rest, a chair-back, and two symmetrical lateral articulated systems performing the function of raising and lowering the seat, the chair-back and the foot-rest, in order to allow the passage of a user of the wheelchair from a sitting position to a standing position.
To this end, each lateral articulated system includes a first deformable polygon or quadrilateral (four-bar linkage) contributing to the support of the seat, composed of two bars, upper and lower respectively, articulated on a front part of the chassis and connected to their rear part by a distance piece.
Each lateral articulated system also includes a second deformable polygon or quadrilateral contributing to the support of the foot-rest, and an articulated chair-back frame on the first quadrilateral opposite to the second quadrilateral, by means of the distance piece at least.
Each articulated lateral system finally includes a manoeuvring assembly, positioned between the first quadrilateral and the chassis, which includes, on the one hand, a first articulated lever on the rear part of the chassis and at the extremity of a second lever whose other extremity is articulated on the first quadrilateral, as well as a manoeuvring handle attached to the second lever. The manoeuvring handle performs a command and control function for the relative pivoting of the lateral system from a lowering position to a raising position of the structure in relation to the chassis and vice versa.
The manoeuvring assembly also includes a device to assist with the raising-lowering movement, such as a pneumatic spring for example. In order to enable it to be gripped easily, regardless of the position of the articulated structure, the manoeuvring handle includes a bow-shaped gripping area which is open at its centre, consisting of two branches connected by a web-linkage, each providing a contact area for the palm of a user's hand.
Such a stand-up type chair completely fulfils the function of raising and lowering its user, who is thereby able to move from a sitting position to a standing position with no assistance, human or mechanical, other than that provided by the pneumatic spring.
Nevertheless, despite the satisfaction obtained through the extreme ease of passage between the two positions, standing and seated, it has appeared necessary, in order to further increase the comfort and convenience of the user, to gear down the movement of the handle in order to reduce its amplitude of motion, so that the handle always remains close to the user, allowing him or her to apply full force during the stand-up movement, which corresponds to a turning motion of the hands during manual movement of the wheelchair.